Umbrella stand base



FIG. 1 is a top perspective view of an umbrella stand base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view, the left side being a mirror image;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown in FIGS. 1-5 are for illustrative purposes only and indicate the nature and use of my new design. The bottom surfaces of the umbrella stand base of my new design to the inside of the broken line circle shown in FIG. 5 are unornamented and are not considered part of my new design. 

The ornamental design for an umbrella stand base, as shown and described. 